Vit Novotny

Optimization of Large-Scale RTCP Feedback Reporting in Fixed and Mobile Networks

RTCP is the accompanying protocol to the RTP, which is very important for the feedback on the control of multimedia streaming services. The bandwidth for RTCP is related to the bandwidth available to the whole session and is limited to 5 %. This fact is a limiting factor for large scale media streaming services based on SSM because of bandwidth sharing among a large number of receivers. The paper describes the hierarchical structure of clients with summarisation nodes in wired and a mobile environment to assure that reporting interval does not exceed the maximum allowed value. Calculations and simulations are presented. The tree structure establishment process is designed.

User performance gains by data offloading of LTE mobile traffic onto unlicensed IEEE 802.11 links

Today, one of the most engaging challenges for mobile operators is the question how to manage the data traffic in mobile networks which is increasing exponentially; mainly due to the growing popularity of applications for mobile devices. Mobile data offloading represents the idea of cost-efficient technology to release the overloaded parts of RAN in cellular networks. This emerging solution introduces the concept of offloading the mobile data from primary cellular communication technology to the IEEE 802.11 infrastructure with aim to gain extra capacity (higher throughput) and improve the overall network performance and user experience. The strategy what, when and for how long to offload data from one communication system to another is non-trivial and therefore already active research in this domain should continue to find the answers for open questions. This paper addresses two the most discussed solutions for offloading between the LTE cellular network and WiFi when the performance needs/requirements exceed the threshold for providing the services via LTE network under an agreed-upon QoS (Quality of Services). In detail, the implementation of SNR (Signal-to-Noise Ratio) threshold based handover and network throughput based handover solutions following the 3GPP standard for Access Network Discovery and Selection Function framework for WiFi offloading in simulation environment NS-3 is proposed. Our simulation results confirm that the concept when the SNR and throughput thresholds can be used to control the mobile data offloading process.

From Standard Definition to High Definition Migration in Current Digital Video Broadcasting

Digital video broadcasting-terrestrial (DVB-T) is important occasion in these days. But HDTV broadcasting is not widely used in Europe in DVB-T nets due high bandwidth requirements. Several solutions of this problem are discussed in this paper. Scalable video coding is the first choice but not very useful. MPEG-4 AVC coding algorithm brings a lot of new features and better compression efficiency also. But differential frame coding is going further. Proposed method can handle a problem with migration from Standard Definition (SD) to High Definition (HD) resolution and saving of the bandwidth in DVB-T nets.

Proposal of a queueing model for simulation of advanced telecommunication services over IMS architecture

This article presents the implementation of a designed model for the simulation of three telecommunication services (File Transfer, Video on Demand and Voice over IP) using a queueing theory. The main objective of this article is modelling and simulations of IMS (IP Multimedia Subsystem) network based on single servers (with a Poisson distribution of job arrivals and an exponential job service time) with FIFO queues of unlimited capacity in Matlab environment. Also, for IMS performance improvement new algorithms for S-CSCF selection were designed and implemented in this mathematical model of IMS subsystem. The results of designed algorithms obtained by simulations are evaluated and compared with each other. It was shown that new algorithms improved IMS performance compared with standardized solution.

Φ-OTDR signal amplification

Phase-sensitive optical time-domain reectometry (Φ-OTDR) seems to be the most appropriate solution for acoustic vibration along standard optical fiber detection. In general the sensing system measures phase changes of the received Rayleigh back-scattered signal in the fiber. Since the back-scattered signal intensity is decreased about tens of decibels in comparison to the forward propagating pulse power level, the received signal power level is very low. That is why the main limiting parameter of the system is the power level of the back-scattered signal, which limits maximum achievable distance. For long reach sensing it is necessary to create high power optical pulses with short time-duration. Direct pulse amplification by erbium doped fiber amplifier (EDFA) is an issue because of the pulses low repetition rate. We have designed and verified a simple method using a holding beam for amplifying of pulses with low repetition rate by standard telecommunication EDFA booster instead of deployment of an expensive optical shutter. A second CW laser with a different wavelength for EDFA stabilization is used in our setup. Because a pulse losses its energy during propagation in the fiber and with longer distances by 1st order Raman amplifier (RA). In telecommunications this amplifier is used to compensate for fiber losses. The second setup uses remote amplification by remotely pumped erbium doped fiber (EDF) placed after a few tens of kilometers of sensing fiber. A pump laser is placed in the transmitter part of the system from where EDF is pumped. In this paper, we present an overview of few techniques for Φ-ODTR signals amplification and their verification by measurement.

Tree Structure for Specific-Source Multicast with Feedback Aggregation

The real time protocol (RTP) and its accompanying real time control protocol (RTCP) are employed in multicast applications. The RTCP protocol is used to distribute feedback on multimedia transmission among session members. The feedback is reported by sending, among others, RR (receiver report) and SR (sender report) packets. With the specific-source multicast, the hierarchical aggregation is used as a method of feedback distribution. The hierarchical aggregation allows a significant reduction of the feedback transmission delay in case of large-scale sessions such as IPTV broadcasting. This paper deals with a tree structure of session members for the feedback distribution with the hierarchical aggregation used. The tree concerned consists of end nodes and summarization nodes. A summarization node aggregates feedback produced from end nodes, which are situated on the lowest tree level only. The tree is applied to an IPTV broadcasting multicast session. The video format used is SD-DVB (standard definition-digital video broadcasting) with the MPEG-2 standard. Also, bandwidth requirements for the feedback distribution in case of the IPTV application described are discussed.

Novel voltage- and current-mode filter design

Demonstrates a new method of active RC filter and oscillator design using modern current-mode circuit elements like general current conveyors (GCCs) and universal current conveyors (UCCs). Several new filter circuits with simulations using SPICE software are presented.

Architecture of a Universal Relation Data Source for Web Applications with Advanced Access Control and Simplified Migration

In enterprise systems many software operations over a database are implemented in a similar way. Systems always take care of correct storage of a data into appropriate tables, data integrity, multilingual support, locales, data validation etc. Data are often stored in a relational database management systems using SQL. SQL standard itself does not provide suitable support for wide range of operations which need to be implemented in almost all cases. Furthermore SQL implementation and triggers/stored procedures programming language differ between various systems. This leads to very difficult migration of software systems based on one database management system to another. Access control provided by the databases is not suitable for an application because users would be allowed to access a database but they must be allowed to access an application instead. Sometimes an application needs to design a more sophisticated access control system. This article deals with this topic and designs an architecture which universally solves all mentioned problem areas. Key benefits it brings are independency on any particular database management system, easy migration to another one and fast fully automatic lowlevel record based rights checking.

Experimental Evaluation of Dynamic Licensed Shared Access Operation in Live 3GPP LTE System

As next-generation mobile networks are rapidly taking shape driven by the target standardization requirements and initial trial implementations, a range of accompanying technologies prepare to support them with more reliable wireless access and improved service provisioning. Among these are more advanced spectrum sharing options enabled by the emerging Licensed Shared Access (LSA) regulatory framework, which aims to efficiently employ the capacity of underutilized frequency bands in a controlled manner. The concept of LSA promises to equip network operators with the much needed additional spectrum on the secondary basis and thus brings changes to the existing cellular network management. Hence, additional research is in prompt demand to determine the required levels of Quality of Service (QoS) and service provisioning reliability, especially in cases of dynamic geographical and temporal LSA sharing. Motivated by this recent urge and having at our disposal a fully-functional 3GPP LTE cellular deployment, we have committed to implement and trial the principles of dynamic LSA-compatible spectrum management. This paper is our first disclosure on the comprehensive experimental evaluation of this promising technology. We expect that these unprecedented practical results together with the key lessons learned will become a valuable reference point for the subsequent integration of flexible LSA-based services, suitable for inter-operator and multi-tenant spectrum sharing.

Image reception and control of IP-cam via digital video broadcasting

The multimedia home platform (MHP) provides a new level of interactivity, which has been standardized with digital video broadcasting DVB. Nowadays, TV watchers can vote, play a game, do shopping or any other things with the DVB-MHP set-top-boxes. This paper describes the universal MHP application for broadcasting, displaying and recording image or video from various distant IP cameras.